Diaphanography is a technique which has been suggested heretofore wherein a human breast is transilluminated with optical or near optical wavelength radiation to produce an image on photographic film for the purpose of detecting lesions. Various approaches to this technique have been proposed, including real time optical viewing, image intensification, video viewing, etc. All of these techniques have the common problem of light scatter, i.e., a very large fraction of the light entering the breast is scattered one or more times prior to exiting the breast. The number of scatters per photon can be quite high and, as a result, the light exiting the breast carriers little or no information about the entrance side of the breast tissue because of the number of scatterings. This has limited diaphanography to imaging the region near the exit plane, and good results have been obtained only by manipulation of the tissue to bring the region of interest as close to the surface as possible.
It has been shown that about 10.sup.-4 of the light incident on a 6 cm. compressed breast will be transmitted without scatter. This means that the mean free path length in a breast is about 0.65 cm., and any object more than 1 cm. below the skin line will be very difficult to detect. Its shadow will diffuse and disappear as the light is scattered. Accordingly, typical techniques now consist of illuminating the breast and mechanically manipulating the skin to try to bring every region of interest within 1 cm. of the skin. This is not easy to do, however, and large fractions of breast tissue which are actually at risk are inaccessible to detection of cancer or lesions by this technique. For these reasons, diaphanography has had limited application heretofore for diagnostic purposes, and has not supplanted other techniques employing X-rays or the like which have the potential of harming a patient that is being examined.